Chemical vapor deposition is currently used to form titanium/titanium nitride film stacks that can be used at the via level. There are several ways to initially deposit the titanium film, including sputtering and chemical vapor deposition. In chemical vapor deposition, the titanium precursor, typically titanium tetrachloride or other titanium tetrahalide, is energized to form elemental titanium which is then deposited on a substrate. A plasma can also be used to excite the titanium. In this method, the plasma, along With for example titanium tetrachioride and hydrogen, are formed into a plasma using RF energy. The plasma is then directed at a substrate and the titanium forms on the substrate.
One problem associated with the deposition of titanium using chemical vapor deposition or plasma enhanced chemical vapor deposition of a titanium halide is the residual halide atoms on the surface of the titanium. Particularly when the titanium is deposited over aluminum, this halide can react with the aluminum forming aluminum halide which has a high resistance. This is a significant problem in via-level applications. This affects the operability, reliability and durability of the formed product.